I have created a chart in CF11 Enterprise, using CFCHART, with clickable drilldown areas by adding the url option with item=$ITEMLABEL$.
This works exactly as it should for the first 10 items on the x-axis, but if there are more items, the values passed to $ITEMLABEL$ beyond the 10th item (and the corresponding value in $VALUE$) do not correspond to the selected item - an earlier value is returned.
The chart axis and data labels are all rendered correctly on the page - its just the values passed by the URL are incorrect after 10 items.
I am pretty sure this is a bug in CF11 (although I can find nothing on this in forums and searches).
I have downloaded a developer edition of ColdFusion 2016 Enterprise, and ran the same code successfully on this server - the correct URL values are passed irrespective of the number of items on the x-axis (well, I tested up to 42).